1. Technical Field
The present invention relates to a torque index sensor. More specifically, the present invention relates to a torque index sensor having improved operational reliability by shielding magnetic field interference between a torque sensor and an index sensor.
2. Related Art
Generally, an electronic power steering (EPS) system is an apparatus for ensuring steering stability of a vehicle, which assists a driver to steer and eases handling by providing a torque in a direction of steering by a driver using a motor.
Such an EPS system may control motor operations according to driving conditions to improve steering performance and steering comfort, unlike the conventional hydraulic power steering (HPS) system.
A torque, steering angle, and steering angle velocity applied to a steering shaft may be measured in order for an EPS system to provide an appropriate torque.
A normal steering structure includes an input shaft combined with a steering wheel, an output shaft combined with a pinion meshed with a rack bar of a wheel side, and a torsion bar connecting the input shaft to the output shaft.
When the steering wheel rotates, a rotational force is transmitted to the output shaft, and a direction of a wheel is changed by functions of the pinion and the rack bar. At this time, when a large amount of resistance is applied, the input shaft rotates more to twist the torsion bar. Here, a magnetic torque sensor measures a degree of twist of the torsion bar.
In addition, an index sensor measures a rotational angular velocity or angular acceleration by detecting rotation of a magnet rotating with the output shaft. Normally, the above-described torque sensor and index sensor may be combined and integrally configured. This is referred to as a torque index sensor.
Such a torque index sensor is simple and economic. However, since the two types of magnetic detecting devices are disposed adjacent to each other, magnetic field interference may occur.
Likewise, if the magnetic field interference between the torque sensor and the index sensor occurs, errors in values measured by the sensors may occur, and thus overall operational reliability may be degraded.